Apparatus and process for feeding slurry



Aug. 28, 1951 w c. DAVIS 2,566,174

, APPARATUS AND PROCESS FOR FEEDING SLURRY I Filed May 16, 1946 'IIIIIIIIII'II'I" IIIIIIIIIIIIIIIIIIIIIII //v VEN TOR W41 TERC 194m" arm CLM A T TORNE) Patented Aug. 28, 1951 APPARATUS AND PROCESS FOR FEEDING SPURRYK Walter C. Davis, Haverford Township, Delaware County, Pa., assignor to The Sharples ration,,a corporation of Delaware Corpo- "Applic'ation May 16, 1946, Serial No:670,243

' The present invention is concerned withan apparatus for intermittently feeding a slurry of solids and liquid and more particularly to an apparatus and process, for feedingamachine designed to dehydrate anddischarge the solids. While the features of the invention may be employed in feeding slurries to machines of varying design, the invention can perhaps best be illustrated by consideration of its application to the feed ofslurries for treatment in the machine of the patent to Brewer, 2,271,493, as the invention was conceived as an arrangement for efiecting feed of slurry to a machine of this type.

In the Brewer patent, slurry is fed from a source of feed through a conduit to a centrifugal rotor in which dehydration takes place, and the feed of the slurry to the machine is controlled by a valve. The machine operates one. timed cycle including a sequence of feeding, rinsing and discharging. operations, and the feed of slurry to the machine is continued onlyduring a part of this cycle. As illustrated in the Brewer patent, the opening and closing of the slurry-feed control valve is accomplished by fluid pressure and spring means.

:,In the feeding of solids to a machine such as illustrated in the Brewer patent, a mixture of liquid and solids is ordinarilypassed to a tank which constitutes a source of feed to the centrifugal rotor, andthe slurry is fed from this source through the above-mentioned conduit and feed valve to said rotor. Difliculty is sometimes encountered inobtaining free flow of the slurry from the source of feed to the centri ugal, particularly after the feed valve has been closed for, a time and solids have had opportunity to, settle andpack in. the conduit, and a feature oithe,

centrifugal rotor. In the practice of the present invention, a special liquid feed line is provided which empties into the, conduit through which the slurry flows to the centrifugal at a point be;- tween the source of feed of such slurry and the slurry-feed control valve, and this supplemental feed of liquid is controlled in such a way that liquid flows into and upward through the slurry.- feed conduit only at such times as the main slurry-feed control valve may be closed. Thus, upward flow of liquid prevents the settling and packing of solids in the feed, conduit and the entrance to it.

The detailed nature of the invention, and fureol i' s. (c1. 210-68l ther features and advantageswill be evident mm? a reading of the following specification in the light-of theattached drawing, in which, Figurel is a flow sheet illustrating the feed of slurry and supplemental. liquid in practice of the,

invention, i

Figure 2 is a side elevation illustrating control of the slurry-feed and supplemental liquid-feed valves, u

Figure 3. is a cross section, partly in elevation, illustrating the detailed control of the slurryfeed valve, and l i a Figure 4 is a View similar to Figure 3, illustrating control of the supplemental liquid-feed valve.

Referring to Figure l of the drawing, the slurry, comprising solids and liquid to be subjected to; centrifugation maybe fed through conduit ID to a source of feedconsisting of a feed tank l l,,. which also acts as asettling tank, and which is provided with a. conduit l2 for decanting off; excess. liquid. The thickenedslurry flows from tank ll through conduit I3 to the centrifugal i4, dehydrated solids being discharged from the cen-. trifugal at l5 and removed liquid separately discharged at I6. A, valve [1 permits intermittent, feed of slurryto the centrifugal, which is of the periodictype as distinguished from a continuous type. i m

In order to assist in the flow of solids to the centrifugalQthere is provided a liquid feed con-.

duit I3, through which supplemental liquid (es g,, mother liquorof crystals under treatment) may be discharged into the conduit [3 at a point 20 between the tank H and valve 11. While this supplemental liquid serves to avoid concentration and packing of the solids in the feed line and thus assistsmaterially in facilitating free flow of the slurry tqthe centrifugal, it is undesirable that an excessive quantity of liquid be fed to the centrifugal since the rate at which solids may be .fed to the centrifugal depends largely upon the amount of liquid fed therewith which must be. separated from the solids during the feeding cycle. This excess liquid must filter through the cake of crystals being built on thescreen and then through the screen, and the rate of passage is limited and controls the rate at which the slurry may be fed.

g In the practice of the present invention, there is provided an apparatus and process by which the feed of supplemental liquid to a portion of the conduit i3 between the tank H and valve ll occurs only during the part of the cycle of operation when the valve I1 is in closed position, and thus prevents flow of slurry to the centrifugal.

The feed of supplemental liquid through conduit l9 to the point 20 is controlled by valve l8, and this valve I8 is maintained in open position when the valve H is in closed position, and vice versa. By this arrangement, supplemental liquid flows into the conduit l3 at the point 20 at such times as the solids cannot pass on through the conduit l3 due to the closing of the valve l l, but flow of supplemental liquid into the conduit I3 is suspended just as soon as the valve I! is opened to permit feed of slurry to the centrifugal. The feed of additional liquid beyond that flowing through the conduit l3 from tank H is thus prevented during the normal slurry feeding portion of the cycle of operations, with the result that the centrifugal operation is not burdened by the necessity of removal of additional liquid introduced at 20 durin this portion of the cycle. The feed of supplemental liquid is accomplished only during the portion of the cycle when such feed is most useful in maintaining the solids in the conduit [3 in a fluid condition, to wit, during the time when the feed to the centrifuge is shut oil. In the practice of the invention, the valves I7 and I8 may be intercon'trolled in the desired manner by use of a three-way valve to effect control in both the slurry-feed conduit and the liquidfeed conduit, or these valves may be operated by the same or separate motors.

Figures 2 to 4 of the drawing illustrate a preferred means for accomplishing control of the valves I? and I8. As illustrated in these figures, fluid pressure from conduit 2| serves to actuate fluid pressure motor 22 controlling valve [8 in conduit l9 and also to actuate fluid pressure motor 23 controlling valve IT in conduit l3.

As illustrated in Figures 3 and 4, the fluid pressure motor 22 causes closure of the valve l8 against the pressure of spring 24 when fluid under pressure is admitted to motor 22. This motor may, for example, be of the familiar diaphragm type and operated by compressed air admitted through conduit 2|. Valve I1 is caused to move to open or flow-permitting position upon admission of fluid under pressure to the motor 23, which may be of the same type as the motor 22, while spring 25 causes closure of this valve upon release of the compressed air or other actuating fluid from the conduit 2|. It will be seen that, when the actuating fluid is admitted under pressure into conduit Zl, the valve H will be opened in opposition to the force exerted by the spring 25 and the valve l8 closed in opposition to the force exerted by the spring 24. Thus, when fluid under pressure is admitted to conduit 2|, the

slurry-feed valve ll will be opened and the supplemental liquid-feed valve it will be closed, while upon release of this pressure, the slurry-feed valve I! will be closed and the supplemental liquid-feed valve [8 will be opened.

Various modifications are available within the.

scope of the invention, and I do not therefore wish to be limited except by the scope of the following claims.

I claim:

1. In an apparatus for feeding a slurry of solids and liquid intermittently to a machine for separating liquid from said solids, the combination comprising a settling tank, a slurry-feed conduit extending from the lower portion of said settling tank to said machine, a slurry-feed valve in said slurry-feed conduit, a liquid-feed conduit interconnected with said slurry-feed conduit at a point upstream from said slurry-feed valve, said liquid.- feed conduit being designed to feed liquid into e said slurry-feed conduit in a direction opposed to the direction of normal flow in said slurry-feed conduit, a liquid-feed valve in said liquid-feed conduit positioned to control feed of liquid from said liquid-feed conduit into said slurry-feed conduit, and a motor for actuating said liquid-feed valve to flow-permitting position when said slurry-feed valve is in flow-preventing position and to flow-preventing position when said slurryfeed valve is in flow-permitting position.

2. Apparatus as defined in claim 1 in which a like motor is employed to actuate said slurry-feed valve.

3. In an apparatus for feeding a slurry of solids and liquid intermittently to a machine for separating liquid from said solids, the combination comprising a settling tank, a slurry-feed conduit extending from the lower portion of said settling tank to said machine, a slurry-feed valve in said slurry-feed conduit, a liquid feed conduit interconnected with said slurry-feed conduit at a point upstream from said slurry-feed valve, said liquidfeed conduit being designed to feed liquid into said slurry-feed conduit in a direction opposed to the direction of normal flow in said slurry-feed conduit, a liquid-feed valve in said liquid-feed conduit positioned to control feed of liquid from said liquid-feed conduit into said slurry-feed conduit, and fluid pressure means for actuating said liquid-feed valve to flow-permitting position when said slurry-feed valve is in fiow-preventing position and to flow-preventing position when said slurry-feed valve is in flow-permitting position.

l. Apparatus as defined in claim 3 in which the fluid pressure system including said fluid pressure means serves also to actuate said slurryfeed valve.

5. In an apparatus for feeding a slurry of solids and liquid intermittently to a machine for separating liquid from said solids, the combination comprising a settling tank, a slurry-feed conduit extending from the lower portion of said settlin tank to said machine, a slurry-feed valve in said slurry-feed conduit, a liquid feed conduit interconnected with said slurry-feed conduit at a point upstream from said slurry-feed valve, said liquidfeed conduit being designed to feed liquid into said slurry-feed conduit in a direction opposed to the direction of normal flow in said slurryfeed conduit, a liquid-feed valve in said liquidfeed conduit positioned to control feed of liquid from said liquid-feed conduit into said slurryfeed conduit, and pneumatic means for actuating said liquid-feed valve to flow-permitting position when said slurry-feed valve is in flow-preventing position, and to flow-preventing position when said slurry-feed valve is in flow-permitting position.

6. Apparatus as defined in claim 5 in which the pneumatic system includin said pneumatic means serves also to actuate said slurry-feed.

valve.

7. A process for intermittently feeding a slurry of solids and liquid to a machine, comprising the steps of establishing a flow of slurry in a feed line to said machine, intermittently interrupting said flow of slurry in said feed line, and, in the course of such interruptions, establishing a reverse flow of a small amount of supplemental liquid in said feed line suflicient to inhibit settling and packing of solids in said feed line.

8. The process of feeding a slurry of solids and liquid from a feed tank to a machine for separating liquid from said solids, comprising the steps of establishing a normal flow of slurry in the feed line to said machine, periodically interrupting said normal flow of slurry, and, in the course of said interruptions, introducing a small amount of supplemental liquid into said feed line sumcient to inhibit settling and packing of solids in said feed line, the introduction of said supplemental liquid into said feed line being in a direction opposed to the direction of normal flow of slurry in said feed line.

9. In an apparatus for feeding a slurry of solids and liquid intermittently, the combination comprising a slurry-feed conduit. means for supplying slurry to said slurry-feed conduit, a slurryfeed valve in said slurry-feed conduit, a liquidfeed conduit interconnected with said slurry-feed conduit at a point upstream from said slurryfeed valve, said liquid-feed conduit being designed to feed liquid into said slurry-feed conduit, a

liquid-feed valve in said liquid-feed conduit posia 6 tioned to control feed of liquid from said liquidfeed conduit into said slurry-feed conduit, and means for actuating said liquid-feed valve to flow permitting position when said slurry-feed valve is in flow-preventing position, and to flow-preventing position when said slurry-feed valve is in flow-permitting position.

WALTER; C; DAVIS.

REFERENCES CITED The following references are of record in the file of this patent: I

UNITED STATES PATENTS Number Name Date 2,271,493 Brewer Jan. .27, 1942 2,310,415 Frymoyer Feb. 9, 1943 2,395,357 Trawick Feb. 19, 1946 2,411,986 Cowherd Dec. 3, 1946 

